Conventionally, well known among microwave surgical devices of this type are those which are equipped with a magnetron (microwave oscillation unit) for generating a microwave and an electrode for irradiating a treatment site being a portion to be heated, with the microwave generated in the magnetron, in a contact state. In such a microwave surgical device, the electrode is set in a contact state with a carcinoma tissue of a patient's liver, for example, and in this state, the microwave is oscillated and irradiated, thereby heating the carcinoma tissue so as to coagulate the tissue.
Herein, the microwave generating unit is that which generates a microwave of a fixed frequency, i.e., 2450 MHz.
In the microwave surgical devices, when progress of a heating process in a treatment site is slow, output of the microwave in the magnetron is increased. Even so, there is a case that a sufficient effect cannot be obtained even if the output is increased. On the other hand, when the treatment site is excessively heated, the treatment site is blackened, and in some cases, even carbonization occurs. As a result, the diseased site may be adversely affected.
Further, the magnetron is that which amplifies and uses the frequency of a certain value or more of an alternate power source. The microwave by the magnetron becomes intermittent output in which a cyclically output 0 state is present in relation to the cycle of the alternate power source (output that is not continuous in time) (see FIG. 8). Thus, there is a problem in that effective heating is not possible. FIG. 8 shows a measurement result of output waveforms of the microwave.